Compressor and pulley for compressor

ABSTRACT

A compressor has a pulley for transmitting torque from an external drive source to a rotary shaft to drive a compression mechanism. The pulley has a pulley body. The compressor has a mass body located in a range that is radially inward of the outer circumference of the pulley. The mass body swings about an axis that is spaced from the rotation axis of the pulley body by a predetermined distance and is substantially parallel to the rotation axis of the pulley body.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a pulley for transmitting torquefrom an external drive source to a rotary shaft thereby driving acompression mechanism. The present invention also pertains to acompressor having such a pulley.

[0002] Typically, a damper mechanism is employed for reducing torquefluctuations in a rotary shaft of a rotation apparatus, therebypreventing resonance. Such a damper mechanism is coupled, for example,to the output shaft of a drive source such as an engine or to the inputshaft of a driven rotational apparatus such as a compressor. When usedin a compressor, a damper mechanism is generally coupled to a rotaryshaft of the compressor, which is coupled to an engine through rotorssuch as a hub and a pulley. Also, a certain type of damper mechanism islocated in a hub or a pulley.

[0003] For example, Japanese Laid-Open Patent Publication No. 9-317628discloses a dynamic damper used in a compressor. The dynamic damperincludes an elastic member and a mass body. The elastic member isattached to one end of the rotary shaft of the compressor. The mass bodyis coupled to the rotary shaft through the elastic member. When therotary shaft is torsionally vibrated due to compression of gas by thepistons, the mass body is resonated to consume the kinetic energy, whichsuppresses the peaks of torque fluctuations caused by the torsionalvibration. Accordingly, resonance generated between the compressor andother devices (external rotational apparatus) is reduced.

[0004] Pendulum type damper mechanisms, which are typically used forengines, are also known in the art. A pendulum type damper mechanismincludes a rotor, which is fixed to the crankshaft of the engine. Apendulum is attached to the rotor. Swinging of the pendulum suppressesthe peaks of torque fluctuations due to torsional vibrations of thecrankshaft. The pendulum swings about an axis that is spaced from therotation axis of the rotor by a predetermined distance and is parallelto the rotation axis of the rotor.

[0005] In the former structure, the mass body, which is accommodated inthe housing, is relatively large and heavy. This increases the weightand the size of the compressor. Also, the mass body is attached to therotary shaft through the elastic member, which is influenced bytemperature changes. Therefore, it is difficult to match thecharacteristic frequency of the dynamic damper with the frequency of thepeaks of the torsional vibrations of the rotary shaft (the frequency ofthe peaks of the torque fluctuations).

[0006] In the latter structure, the pendulum is connected to thecrankshaft through the rotor, which increases the weight and the size ofthe rotor.

[0007] In the dynamic damper disclosed in Japanese Laid-Open PatentPublication No. 2000-274489, each of roller mass bodies reciprocatesalong a cylindrical path.

[0008] The mass body is accommodated in a guiding portion (accommodationchamber) formed in the rotor. Part of the inner surface of the guideportion is formed as a part of the inner surface of a cylinder. Thecenter of curvature of the cylinder is an axis that is spaced from therotation axis of the rotor by a predetermined distance and is parallelto the rotation axis of the rotor. When the rotor rotates, centrifugalforce presses the mass body against the cylinder inner surface. In thisstate, torque fluctuations of the rotary shaft are received by the rotorand swing the mass body along the cylinder inner surface.

[0009] Sliding movement of the mass body on the cylinder inner surfacewears the mass body and the cylinder inner surface, or the rotor. Thiswill change the shape of the mass and the shape of the cylindrical innersurface. As a result, the settings for effectively preventing resonanceare changed, which degrades the resonance prevention performance.Further, the wear shortens the life of the rotor, or the rotationapparatus.

SUMMARY OF THE INVENTION

[0010] Accordingly, it is an objective of the present invention toprovide a compressor having a compact and light pulley that is easilyadjusted to reduce resonance. Another objective of the present inventionis to provide a compressor that prevents its resonance reductionperformance from deteriorating and its life from being shortened.

[0011] To achieve the foregoing and other objectives and in accordancewith the purpose of the present invention, a compressor is provided. Thecompressor has a pulley for transmitting torque from an external drivesource to a rotary shaft to drive a compression mechanism. The pulleyhas a pulley body. The compressor comprises a mass body located in arange that is radially inward of the outer circumference of the pulley.The mass body swings about an axis that is spaced from the rotation axisof the pulley body by a predetermined distance and is substantiallyparallel to the rotation axis of the pulley body.

[0012] The present invention also provides a pulley for a compressor.The pulley comprises a pulley body and a mass body. The mass body islocated in a range that is radially inward of the outer circumference ofthe pulley. The mass body swings about an axis that is spaced from therotation axis of the pulley body by a predetermined distance and issubstantially parallel to the rotation axis of the pulley body.

[0013] Other aspects and advantages of the invention will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention, together with objects and advantages thereof, maybest be understood by reference to the following description of thepresently preferred embodiments together with the accompanying drawingsin which:

[0015]FIG. 1 is a cross-sectional view illustrating a compressoraccording to a first embodiment of the present invention;

[0016]FIG. 2(a) is a front view illustrating a pulley body attached tothe compressor of FIG. 1;

[0017]FIG. 2(b) is a cross-sectional view taken along line 2 b-2 b ofFIG. 2(a);

[0018]FIG. 3(a) is a front view illustrating a pulley according to asecond embodiment of the present invention;

[0019]FIG. 3(b) is a cross-sectional view taken along line 3 b-3 b ofFIG. 3(a);

[0020]FIG. 4(a) is a front view illustrating a pulley according to athird embodiment of the present invention;

[0021]FIG. 4(b) is a cross-sectional view taken along line 4 b-4 b ofFIG. 4(a);

[0022]FIG. 5 is a partial front view illustrating a pulley bodyaccording to a fourth embodiment of the present invention;

[0023]FIG. 6(a) is a partial front view illustrating a pulley bodyaccording to a fifth embodiment of the present invention;

[0024]FIG. 6(b) is a cross-sectional view taken along line 6 b-6 b ofFIG. 6(a);

[0025]FIG. 7(a) is a perspective view illustrating a pendulum accordingto a sixth embodiment of the present invention;

[0026]FIG. 7(b) is a perspective view illustrating a roller according toa seventh embodiment of the present invention;

[0027]FIG. 8 is a partial front view illustrating a pulley bodyaccording to an eighth embodiment of the present invention; and

[0028]FIG. 9 is an cross-sectional view illustrating a pulley accordingto a ninth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] A compressor C according to a first embodiment of the presentinvention will now be described with reference to FIGS. 1 to 2(b). InFIG. 1, the left end of the compressor C is defined as the front end,and the right end of the compressor C is defined as the rear end.

[0030] As shown in FIG. 1, the compressor C includes a cylinder block11, front housing member 12 and a rear housing member 14. The fronthousing member 12 is secured to the front end face of the cylinder block11. The rear housing member 14 is secured to the rear end face of thecylinder block 11, and a valve plate assembly 13 is located between therear housing member 14 and the rear end face. The cylinder block 11, thefront housing member 12, the valve plate assembly 13, and the rearhousing member 14 form the housing of the compressor C.

[0031] The cylinder block 11 and the front housing member 12 define acrank chamber 15. A rotary shaft, which is a drive shaft 16 in thisembodiment, extends through the crank chamber 15. The drive shaft 16 isrotatably supported.

[0032] The front housing member 12 has a cylindrical wall 40, whichextends forward. The front end of the drive shaft 16 is located in thecylindrical wall 40, and is connected to an external drive source, whichis an engine E in this embodiment, through a pulley 17 and a belt 18engaged with the pulley 17.

[0033] A lug plate 19 is fixed to the drive shaft 16 and is located inthe crank chamber 15. A swash plate 20 is also accommodated in the crankchamber 15. The swash plate 20 slides along and inclines relative to theaxis of the drive shaft 16. A hinge mechanism 21 is located between thelug plate 19 and the swash plate 20. The hinge mechanism 21 and the lugplate 19 cause the swash plate 20 to rotate integrally with the driveshaft 16.

[0034] The minimum inclination angle of the swash plate 20 is defined bya snap ring 22, which is fixed to the drive shaft 16, and a spring 23,which extends between the snap ring 22 and the swash plate 20. Theminimum inclination angle of the swash plate 20 is an angle of the swashplate 20 when the angle defined by the swash plate 20 and the axis ofthe drive shaft 16 is the closest to the ninety degrees.

[0035] Cylinder bores 24 (only one is shown in FIG. 1) are formed in thecylinder block 11 at constant angular intervals about the axis of thedrive shaft 16. Each cylinder bore 24 accommodates a single headedpiston 25 such that the piston 25 can reciprocate in the cylinder bore24. The opening of each cylinder bore 24 is covered by the valve plateassembly 13 and the corresponding piston 25. A compression chamber isdefined in each cylinder bore 24. The volume of each compression chambervaries in accordance with the reciprocation of the corresponding piston25. The front end of each piston 25 is coupled to the periphery of theswash plate 20 through a pair of shoes 26. The swash plate 20 is rotatedas the drive shaft 16 rotates. Rotation of the swash plate 20 isconverted into reciprocation of each piston 25 by the corresponding pairof shoes 26.

[0036] The drive shaft 16, the lug plate 19, the swash plate 20, thehinge mechanism 21, the pistons 25, and the shoes 26 form a piston typecompression mechanism.

[0037] A suction chamber 27 and a discharge chamber 28 are definedbetween the valve plate assembly 13 and the rear housing member 11. Thedischarge chamber 28 is located around the suction chamber 27. Suctionports 29 and discharge ports 31 are formed in the valve plate assembly13. Each suction port 29 and each discharge port 31 correspond to one ofthe cylinder bores 24. Suction valve flaps 30 and discharge valve flaps32 are also formed in the valve plate assembly 13. Each suction valveflap 30 corresponds to one of the suction ports 29. Each discharge valveflap 32 corresponds to one of the discharge ports 31. Each cylinder bore24 is connected to the suction chamber 27 through the correspondingsuction port 29. Each cylinder bore 24 is also connected to thedischarge chamber 28 through the corresponding discharge port 31.

[0038] When each piston 25 moves from the top dead center position tothe bottom dead center position, refrigerant gas in the suction chamber27 is drawn into the corresponding compression chamber through thecorresponding suction port 29 while flexing the corresponding suctionvalve flap 30 to an open position. As the piston 25 is moved from thebottom dead center position to the top dead center position, therefrigerant gas is compressed to a predetermined pressure and isdischarged to the discharge chamber 28 through the correspondingdischarge port 31 while flexing the corresponding discharge valve flap32 to an open position.

[0039] The suction chamber 27 is connected to the discharge chamber 28through an external refrigerant circuit (not shown). Refrigerantdischarged from the discharge chamber 28 flows to the externalrefrigerant circuit. In the circuit, heat exchange through refrigeranttakes place. Refrigerant discharged from the circuit is drawn into thesuction chamber 27, and then drawn into the cylinder bores 24 to becompressed again.

[0040] A bleed passage 33 is formed in the compressor housing to connectthe crank chamber 15 with the suction chamber 27. A supply passage 34 isalso formed in the compressor housing to connect the discharge chamber28 with the crank chamber 15. The supply passage 34 is regulated by acontrol valve 35, which is located in the supply passage 34.

[0041] The opening of the control valve 35 is adjusted to control theflow rate of highly pressurized gas supplied to the crank chamber 15through the supply passage 34. The pressure in the crank chamber 15, orcrank chamber pressure Pc, is determined by the ratio of the refrigerantgas supplied to the crank chamber 15 through the supply passage 34 andthe flow rate of refrigerant gas conducted out from the crank chamber 15through the bleed passage 33. As the crank chamber pressure Pc varies,the difference between the crank chamber pressure Pc and the pressure inthe compression chambers, which changes the inclination angle of theswash plate 20. Accordingly, the stroke of each piston 25, or thecompressor displacement, is varied.

[0042] As shown in FIGS. 1 and 2(b), the pulley 17 is supported by thecylindrical wall 40 with a bearing 41. The pulley 17 is coupled to thefront end of the drive shaft 16 and rotates integrally with the driveshaft 16.

[0043] As shown in FIGS. 1 to 2(b), the pulley 17 has a pulley body 42,a boss 43, which is fitted to the outer ring of the bearing 41, and abelt receiving portion 44, to which the belt 18 is engaged. An annularrecess 45 is formed in the pulley body 42 between the boss 43 and thebelt receiving portion 44. A mass body, which is a rigid pendulum 46 inthis embodiment, is located in the recess 45.

[0044] The rigid pendulum 46 is attached to the pulley body 42 by asupport shaft 47, which is fixed to the boss 43 of the pulley body 42and extends through a hole 46A formed in the rigid pendulum 46. Therigid pendulum 46 swings about the support shaft 47. A wear reductionmember, which is fluorocarbon resin coating 48 in this embodiment, isformed on the inner surface of the hole 46A to reduce wear of the hole46A due to contact with the support shaft 47. In FIG. 2(b), thefluorocarbon resin coating 48 is exaggerated for purposes ofillustration. The support shaft 47 is spaced from the rotation axis ofthe pulley body 42 by a predetermined distance. The axis of the supportshaft 47 is parallel to the rotation axis of the pulley body 42. Therotation axis of the pulley body 42 is aligned with the axis of thedrive shaft 16. A head is formed at the distal end of the support shaft47. The diameter of the head is greater than that of the hole 46A. Thehead thus prevents the rigid pendulum 46 from coming off the supportshaft 47.

[0045] The rigid pendulum 46 functions as a centrifugal pendulum whenthe pulley body 42 rotates. In this embodiment, the position, the shape,and the mass of the rigid pendulum 46 are determined such that swingingof the rigid pendulum 46 reduces torque fluctuations due to torsionalvibrations of the drive shaft 16.

[0046] Settings of the rigid pendulum 46 will now be described. Therigid pendulum 46 reduces torque fluctuation the frequency of which isequal to the characteristic frequency of the pendulum 46. Therefore,determining the characteristics of the pendulum 46 such that thecharacteristic frequency of the pendulum 46 is equal to the frequency ofthe peaks of torque fluctuations reduces the torque fluctuations. Thepeaks of the torque fluctuations refer to components at orderfrequencies.

[0047] The frequency of torque fluctuations and the characteristicfrequency of the rigid pendulum 46 are proportionate to the angularvelocity ω₁, of the drive shaft 16, which correlates with the rotationspeed of the drive shaft 16. The frequency of the greatest peak oftorque fluctuations of the compressor C is represented by a product(ω₁/2π) N of the rotation speed of the drive shaft 16 (ω₁/2π) and thenumber N of the cylinder bores 24. Through experiments, it has beendiscovered that the frequency of an nth (n is a natural number) greatestpeak of the torque fluctuation of the compressor C tends to be equal tothe product n(ω₁/2π)N.

[0048] The characteristic frequency of the rigid pendulum 46 isrepresented by the product of the rotation speed (ω₁/2π) of the driveshaft 16 and the square root of the ratio R/r. R is the distance betweenthe rotation axis of the pulley body 42 and the axis of the pendulum 46,or the axis of the support shaft 47, and r is the distance between theaxis of the pendulum 46 and the center of gravity of the pendulum 46.

[0049] Therefore, the frequency of the nth greatest peak of torquefluctuations can be matched with the characteristic frequency of therigid pendulum 46 by equalizing the ratio R/r with the product nN.Accordingly, the nth greatest peak of the torque fluctuation will bereduced.

[0050] In this embodiment, the distances R and r are determined suchthat the square root of the ratio R/r is equal to the number nN when then is one. This construction reduces the greatest peak of the torquefluctuations.

[0051] To effectively reduce torque fluctuations by swinging of thependulum 46, the torque T about the rotation axis of the pulley body 42applied by the pendulum 46 needs to be equal to the amplitude of thetorque fluctuations so that the torque T acts against the amplitude.When the frequency of the peak of torque fluctuations is equal to thecharacteristic frequency of the pendulum 46, the torque T is representedby the following equation.

T=m (ω_(a))²(R+r)Rφ  (Equation 1)

[0052] Sign m represents the mass of the pendulum 46, ω_(a) is theaverage angular velocity of the pendulum 46 when swinging within a smallangle φ.

[0053] In this embodiment, the mass m is maximized so that the values R,r and φ are minimized. As a result, the torque T is maximized withoutincreasing the size of the pulley body 42.

[0054] Various settings are made in the assumption that the pendulum 46is a mass point at the center of gravity.

[0055] The operation of the compressor C will now be described.

[0056] When force is supplied to the drive shaft 16 from the engine Ethrough the pulley 17, the drive shaft 16 rotates together with theswash plate 20. As the swash plate 20 rotates, each piston 25 isreciprocated by a stroke that corresponds to the inclination angle ofthe swash plate 20. As a result, refrigerant is repeatedly drawn into,compressed in and discharged from each cylinder bore 24.

[0057] When the opening degree of the control valve 35 is decreased, theflow rate of refrigerant gas that is supplied from the discharge chamber28 to the crank chamber 15 through the supply passage 34 is decreasedaccordingly. As a result, the crank chamber pressure Pc is lowered andthe inclination angle of the swash plate 20 is increased, whichincreases the displacement of the compressor C. When the opening degreeof the control valve 35 is increased, the flow rate of refrigerant gasthat is supplied from the discharge chamber 28 to the crank chamber 15through the supply passage 34 is increased. As a result, the crankchamber pressure Pc is increased and the inclination angle of the swashplate 20 is decreased, which decreases the displacement of thecompressor C.

[0058] When rotating, the drive shaft 16 receives compression reactionforce of refrigerant and reaction force of the reciprocation of thepistons 25 through the swash plate 20 and the hinge mechanism 21. Thiscreates torsional vibrations in the drive shaft 16. The torsionalvibration creates torque fluctuations. The torque fluctuations produceresonance in the compressor C and in external rotation apparatus such asthe engine E and other auxiliary devices, which are coupled to thecompressor C through the pulley 17 and the belt 18.

[0059] Torque fluctuations cause the rigid pendulum 46 in the pulley 17to start swinging. Accordingly, torque applied about the rotation axisof the pulley body 42 reduces the torque fluctuations. Thecharacteristic frequency of the pendulum 46 is set equal to thefrequency of the greatest peak of the torque fluctuation. Therefore, thegreatest peak is reduced and the torque fluctuation of the pulley 17 iseffectively reduced. As a result, resonance caused by the torquefluctuations is effectively reduced.

[0060] This embodiment has the following advantages.

[0061] (1) The rigid pendulum 46 in the pulley body 42 swings to reducetorsional vibration. As a result, resonance produced in the pulley body42, the compressor C, and the rotation apparatus coupled to the pulleybody 42 through the belt 18 is reduced.

[0062] The structure for reducing resonance is located in the pulley 17.Therefore, there is no need to provide a resonance reduction mechanismon the drive shaft 16, to which the pulley 17 is coupled. This reducesthe weight and the size of the compressor C.

[0063] For example, compared to a case where a mass body is attached toa rotary shaft connected to a pulley body through an elastic member forreducing resonance, the structure of the above illustrated embodiment isless susceptible to temperature changes. Therefore, the characteristicfrequency of the pendulum 46 can be easily matched with the frequency ofthe peak of the torque fluctuations.

[0064] Compared to a case where a mass body is directly attached to arotary shaft connected to a pulley body and a case where a mass body isattached to a rotary shaft connected to a pulley body through an elasticmember, the size and the weight of the mass body are decreased in theabove illustrated embodiment. Thus, the structure for reducing resonanceis compact and light.

[0065] (2) The rigid pendulum 46 moves in a range that is radiallyinward of the outer circumference of the pulley body 42. In other words,the pendulum 46 does not project beyond the circumference of the pulleybody 42. Therefore, the structure for reducing resonance occupiesrelatively small space.

[0066] (3) The pendulum 46 is rotatably supported by the pulley body 42through the support shaft 47, which extends through the hole 46A. A massbody, such as a pendulum, may be coupled to the pulley body 42 through aflexible member. However, when the centrifugal force due to the rotationof the pulley body 42 is less than the gravity and the mass body islocated above the rotation axis of the pulley body 42, the mass body maycollide with a part that is located radially inward of the mass body.The collision produces noise. In the above illustrated embodiment, thependulum 46 is directly supported by the pulley body 42 without anyelastic members in between. Therefore, the pendulum 46 produces nonoise.

[0067] (4) The fluorocarbon resin coating 48 is formed on the innersurface of the hole 46A to reduce friction between the hole 46A and thesupport shaft 47. The coating 48 reduces friction resistance between thesupport shaft 47 and the pendulum 46, and therefore reduces the wear atthe contact portions. In other words, the support shaft 47 and thependulum 46 are scarcely deformed by wear. This prevents the resonancereduction performance from deteriorating and extends the life of thepulley 17.

[0068] A pulley 60 according to a second embodiment of the presentinvention will now be described with reference FIGS. 3(a) and 3(b).Mainly, the differences from the pulley 17 illustrated in FIGS. 1 to2(b) will be discussed below.

[0069] As shown in FIG. 3(b), the pulley 60 includes a boss 62 and abelt receiving portion 63. The boss 62 is fitted about the outer ring ofthe bearing 41. The belt 18 is engaged with the belt receiving portion63. Two guide portions, which are two recesses 64 in this embodiment,are formed in a pulley body 61 of the pulley 60. The recesses 64 arelocated between the boss 62 and the belt receiving portion 63. Therecesses 64 are symmetric with respect to the rotation axis of thepulley body 61.

[0070] A guide surface 65 is formed in each recess 64. Each guidesurface 65 has an arcuate cross section and is located at the radiallyouter portion of the recess 64. Each guide surface 65 is included in animaginary circle. The center of the imaginary circle is spaced from therotation axis of the pulley body 61 by a predetermined distance R₁ andparallel to the rotation axis of the pulley body 61. The radius of thecircle is represented by r₁.

[0071] Each recess 64 includes an auxiliary guide surface 66, which isformed in the radially inner surface and is spaced from the guidesurface 65 by a predetermined distance. The auxiliary guide surface 66has an arcuate cross section. As shown in FIG. 3(a), the center of eachrecess 64 is located radially outside than the ends. Each recess 64 hasconstant width. Each recess 64 is symmetric with respect to a line thatincludes the rotation axis of the pulley body 61 and the center of thecorresponding imaginary circle.

[0072] A cylindrical rigid roller 67 is accommodated in each recess 64.The roller 67 has a circular cross section. The mass of each roller 67is represented by m₁. The diameter d₁ of each roller 67 is slightly lessthan the distance between the corresponding guide surface 65 and thecorresponding auxiliary guide surface 66. The length of each roller 67along the axial direction of the pulley 60 is slightly less than thelength of the corresponding recess 64 along the same direction. That is,each roller 67 can move along the corresponding guide surface 65 in thecorresponding recess 64. An annular lid 68 is fixed to the boss 43 bybolts (not shown) to cover the opening of each recess 64. The lid 68prevents the rollers 67 exiting the recesses 64. A wear reductionmember, which is fluorocarbon resin coating 48 in this embodiment, isformed on the surface of each roller 67. In FIG. 3(b), the fluorocarbonresin coating 48 is exaggerated for purposes of illustration. Thecoating prevents the surface of the roller 67 from being worn due tocontact with the surface of the recess 64 and the inner surface of thelid 68.

[0073] When the compressor C is operated by the engine E, each roller 67contacts the corresponding guide surface 65 due to centrifugal force. Iftorque fluctuations occur in this state, each roller 67 reciprocatesalong the guide surface 65 in the corresponding recess 64. That is, eachroller 67, or its center of gravity, moves in a manner that iscomparable with the movement of the pendulum 46 of the embodimentillustrated in FIGS. 1 to 2(b). In other words, the rollers 67 functionas centrifugal pendulum when the compressor C is operated by the engineE.

[0074] In this embodiment, the center of each imaginary circle, whichincludes one of the guide surfaces 65, is aligned with the axis of theswinging motion of the corresponding roller 67. That is, the distance R₁between the rotation axis of the pulley body 61 and the center of eachimaginary circle corresponds to the distance R in the embodimentillustrated in FIGS. 1 to 2(b).

[0075] The distance between the center of swinging motion of each roller67 and the center of gravity of the roller 67 is equal to the differencebetween the radius r₁ of the imaginary circle and one-half the diameterd₁ of each roller 67. That is, the difference (r₁−(d₁/2)) corresponds tothe distance r in the embodiment illustrated in FIGS. 1 to 2(b).

[0076] In this embodiment, the values R₁, r₁ and d₁ are determined suchthat the square root of the ratio R₁/(r₁−d₁/2)) is equal to the number Nwhen the n is one for reducing the greatest peak of torque fluctuations.

[0077] A value that corresponds to the value m of the equation 1 is thetotal mass of the rollers 67, or 2m₁.

[0078] In this embodiment, the total mass 2m₁ of the rollers 67 ismaximized so that the values R₁, (r₁−(d₁/2)) and φ are minimized. As aresult, the torque T is maximized without increasing the size of thepulley body 42.

[0079] As in the embodiment illustrated in FIGS. 1 to 2(b), varioussettings are made in the assumption that each roller 67 is a mass pointat the center of gravity.

[0080] In addition to the advantages (1) and (2) of the firstembodiment, the second embodiment has the following advantages.

[0081] (5) The recesses 64 are formed in the pulley body 61 and eachhave the guide surface 65, which has an arcuate cross section. Eachrigid roller 67, which has a circular cross section, moves along thecorresponding guide surface 65. If a mass body is supported at a fulcrumby a support shaft, the distance between the center of swinging of themass body, or the fulcrum, and the center of gravity of the mass body isvaried due to the space created between the support shaft and a holeformed in the mass body for receiving the support shaft. However, in thesecond embodiment, the rollers 67 are not supported by fulcrums ofswinging. The distance between the center of swinging, or fulcrum, andthe center of gravity of the mass body is constant. Therefore, resonanceis reliably reduced.

[0082] (6) In the pulley body 61, two rollers 67 swing. Compared to acase where a single roller swings, the total mass is greater in thesecond embodiment. That is, the value that corresponds to the value m inthe equation 1 is increased. Therefore, the torque T is increasedwithout increasing the size of the pulley body 61.

[0083] (7) The fluorocarbon resin coating 48 is formed on the surface ofeach roller 67 to reduce wear due to contact with the surface of therecess 64 and the lid 68. Since the coating 48 friction resistancebetween each roller 67 and the pulley body 61, wear at the contactportions is reduced. In other words, the rollers 67 and the pulley body61 are scarcely deformed by wear. This improves the resonance reductionperformance and extends the life of the pulley 60.

[0084] A pulley 60 according to a third embodiment of the presentinvention will now be described with reference FIGS. 4(a) and 4(b).Mainly, the differences from the pulley 17 illustrated in FIGS. 3(a) and3(b) will be discussed below.

[0085] As shown in FIG. 4(a), guide portions, which are six recesses 80in this embodiment, are formed in the pulley body 61. The recesses 80are angularly spaced by constant intervals. Compared to the recesses 64in the embodiment of FIGS. 3(a) and 3(b), each recess 80 is wide in thecircumferential direction. Particularly, the circumferential size ofeach recess 80 is increased toward the center of the pulley body 61. Ineach recess 80, the circumferential dimension is not uniform.

[0086] A guide surface 82 is formed in the radially outer portion ofeach recess 80. Each guide surface 82 has an arcuate cross section. Eachguide surface 82 is included in an imaginary circle. The center of theimaginary circle is spaced from the rotation axis of the pulley body 61by a predetermined distance R₂ and the radius of the circle isrepresented by r₂.

[0087] A cylindrical rigid roller 83 is accommodated in each recess 80.The roller 83 has a circular cross section. The mass of each roller 83is represented by m₂. The diameter of each roller 83 is represented byd₂. A wear reduction member, which is fluorocarbon resin coating 48 inthis embodiment, is formed on the surface of each roller 83. In FIG.4(b), the fluorocarbon resin coating 48 is exaggerated for purposes ofillustration. The coating prevents the surface of the roller 83 frombeing worn due to contact with the surface of the recess 80 and theinner surface of the lid 68.

[0088] As in the rollers 67 of the embodiment illustrated in FIGS. 3(a)and 3(b), each roller 83 contacts the corresponding guide surface 82 dueto centrifugal force when the compressor C is operated by the engine E.If torque fluctuations occur in this state, each roller 83 reciprocatesalong the guide surface 82 in the corresponding recess 80. That is, eachroller 83 moves in a manner that is comparable with the movement of thependulum 46 of the embodiment illustrated in FIGS. 1 to 2(b).

[0089] The values R₂, r₂, and d₂ correspond to the values R₁, r₁, and d₁in the embodiment of FIGS. 3(a) and 3(b), respectively. The distancesR₂, r₂ and d₂ are determined such that the square root of the ratioR₂/(r₂−d₂/2)) is equal to the number N when the n is one for reducingthe greatest peak of torque fluctuations.

[0090] A value that corresponds to the value m of the equation (1) isthe total mass of the rollers 83, or 6m₂.

[0091] In this embodiment, the total mass 6m₂ of the rollers 83 ismaximized so that the values R₂, (r₂−(d₂/2)) and φ are minimized. As aresult, the torque T is maximized without increasing the size of thepulley body 61.

[0092] As in the embodiments illustrated in FIGS. 1 to 3(b), varioussettings are made in the assumption that each roller 83 is a mass pointat the center of gravity.

[0093] In addition to the advantages (1), (2), (5), (6), and (7) of theabove illustrated embodiments, the third embodiment has the followingadvantages.

[0094] (8) Compared to the embodiment of FIGS. 3(a) and 3(b), the numberof the mass bodies, or the rollers 83, is increased to six. The numberof the recesses 80 is also six. Therefore, the torque T is increasedwithout increasing the size of the pulley body 61.

[0095] (9) Compared to the embodiment of FIGS. 3(a) and 3(b), thecircumferential dimension of each recess 80 increases toward therotation axis of the pulley body 61. This structure permits the diameterand the mass of each roller 83 to be increased. Therefore, the torque Tis further increased.

[0096] A fourth embodiment of the present invention will now bedescribed with reference FIG. 5. Mainly, the differences from theembodiment of FIGS. 3(a) and 3(b) will be discussed below.

[0097]FIG. 5 illustrates a pulley body 61 before being attached to thedrive shaft 16. Also, in FIG. 5, the roller 67 and the lid 68 have notbeen installed in the pulley body 61. A sintered member 65A, whichcontains lubricant, is attached to the guide surface 65. The innersurface 65B of the sintered member 65A contacts the corresponding roller67. The lubricant in the sintered member 65A reduces the frictionresistance between the roller 67 and the surface 65B. Therefore, wear ofthe contact portions is reduced.

[0098] A fifth embodiment of the present invention will now be describedwith reference to FIGS. 6(a) and 6(b).

[0099] FIGS. 6(a) and 6(b) illustrate a pulley body 61 before beingattached to the drive shaft 16. Also, in FIGS. 6(a) and 6(b), the roller67 and the lid 68 have not been installed in the pulley body 61. Anaccommodation recess 61B is formed in a portion of the pulley body 61between the boss 62 and the belt receiving portion 63. The accommodationrecess 61B accommodates a guide block 64B. The guide block 64B is asintered member containing lubricant. A roller recess 64C is formed inthe guide block 64B to receive the roller 67. The lubricant in the guideblock 64B reduces the friction resistance between the roller 67 and thesurface of the roller recess 64C. Therefore, wear of the contactportions is reduced.

[0100] A sixth embodiment according to the present invention will now bedescribed with reference to FIG. 7(a). In this embodiment, the hole 46Aof the rigid pendulum 46, to which the support shaft 47 is inserted, isformed in a sintered cylinder 46B containing lubricant. The lubricant inthe cylinder 46B reduces the friction resistance between the supportshaft 47 and the cylinder 46B. Therefore, wear of the contact portionsis reduced.

[0101] A seventh embodiment according to the present invention will nowbe described with reference to FIG. 7(b). The differences from theembodiment of FIGS. 3(a) and 3(b) will be discussed. In the seventhembodiment, a sintered layer 67A containing lubricant is formed on thecircumference of the roller 67, which contacts the guide surface 65. Thelubricant in the layer 67A reduces wear between the guide surface 65 andthe roller 67. In the embodiment of FIGS. 4(a) and 4(b), the surface ofeach roller 83 may be formed with a sintered material.

[0102] An eighth embodiment according to the present invention will nowbe described with reference to FIG. 8. The differences from theembodiment of FIG. 3(a) will be discussed. FIG. 8 illustrates a pulleybody 61 before being attached to the drive shaft 16. Also, in FIG. 8,the roller 67 and the lid 68 have not been installed in the pulley body61. A wear reduction member, which is a metal collar 64A in thisembodiment, is fitted to the recess 64 to form the guide surface 65 andthe auxiliary guide surface 66. Except for the collar 64A, the pulleybody 61 is made of resin. In this embodiment, a lid (not shown) isattached to the pulley body 61 to prevent the collar 64A from escaping.The lid may be made of metal or resin. Since the pulley body 61 is madeof resin except for the metal collar 64A, the weight of the pulley body61 is reduced compared to a case where the pulley body 61 is made ofmetal. Since the guide surface is formed of metal, the guide surface isless prone to wear. The guide surface 82 illustrated in FIGS. 4(a) and4(b) may be formed of metal.

[0103] In the embodiments illustrated in FIGS. 3(a) to 4(b), the lid 68is coupled to the pulley body 61 by bolts. However, the lid 68 may beattached to the pulley body 61 by means other than bolts. For example,crimping pins or press fitting pins may be used. Such pins are insertedinto holes formed in the lid 68 and corresponding holes formed in thepulley body 61. An end of a crimping pin is crimped so that it does notescape the corresponding holes. A press fitting pin is press fitted intothe corresponding holes. For example, in a ninth embodiment illustratedin FIG. 9, a pin 90 having an elastic portion 90A is used. FIG. 9 is aschematic cross-sectional view illustrating the pulley 60. A hole 68A isformed in the lid 68 and a hole 61A is formed in the pulley body 61 tocorrespond to the hole 68A. The diameter of the hole 61A issubstantially the same as that of the hole 68A. The pin 90 extendsthrough the holes 68A and 61A. The main portion 90B of the pin 90 iscylindrical and has substantially the same diameter as the diameter ofthe holes 61A, 68A. A head 90C, the diameter of which is greater thanthat of the hole 68A is formed integrally with the main portion 90B atone end. Engaging pieces 90A (only two of them are shown in FIG. 9) areformed integrally with the main portion 90B at the other end of the mainportion 90B. In the normal state, each engaging piece 90A is taperedtoward the distal end. In this state, the distal end of each engagingportion 90A is located radially outside of the opening of the hole 61A.Therefore, the engaging portions 90A and the head 90C prevent the pin 90from escaping the holes 61A, 68A, and the lid 68 is secured to thepulley body 61. The engaging portions 90A can be elastically deformed byexternal force. When the engaging portions 90A are deformed, theproximal ends are radially inward of the holes 61A, 68A. That is, thepin 90 can be inserted into and removed from the holes 61A, 68A bydeforming the engaging portions 90A. When securing the lid 68 to thepulley body 61 by using the pin 90, the pin 90 need not be rotated orcrimped, which facilitates the installation.

[0104] The present invention may be embodied in the following forms.

[0105] In the embodiment of FIGS. 1 to 2(b), the pendulum 46 may includea support shaft and the support shaft may be inserted into the hole 46Aformed in the pulley body 42.

[0106] In the embodiment of FIGS. 1 to 2(b), an additional rigidpendulum that is similar to the pendulum 46 may be used. In this case,the additional pendulum is located symmetrically from the rigid pendulum46 with respect to the rotation axis of the pulley body 42.Alternatively, the number of the pendulum 46 may be increased to threeor more. In this case, the pendulums 46 are angularly spaced at theconstant intervals.

[0107] In some cases, the center of gravity of the pulley body 42 isdisplaced by the pendulum 46. In the embodiment of FIGS. 1 to 2(b), abalancer such as a counter weight may be located in the pulley body 42to balance the center of gravity of the pulley body 42. Alternatively, anotch may be formed in the pulley body 42.

[0108] In the embodiments of FIGS. 3(a) to 4(b), the cross-sectionalshape of each recess 64, 80 may be circular. In this case, the guidesurface 65, 82 is formed as a part of the circular recess 64, 80. Thisstructure facilitates the formation of the recess 64, 80.

[0109] In the embodiments of FIGS. 3(a) to 4(b), the rollers 67, 83 maybe replaced by balls.

[0110] In the embodiments shown in FIGS. 1 to 9, the square root of theratio R/r is set equal to nN in which n is one, or to N. However, thesquare root of the ratio R/r may be set equal to nN in which n is two ora greater natural number.

[0111] In the embodiments of FIGS. 1 to 9, the number of mass bodies(the pendulum 46, the roller 67, 83) may be two or more. The number ofmass need not correlate the number of the cylinder bores 24 of thecompressor C.

[0112] Two or more of the pendulum 46, the roller 67, 83 may be used ina single pulley.

[0113] In the embodiments of FIGS. 1 to 9, various settings are made onthe assumption that the mass body is a mass point at the center ofgravity. However, various settings are preferably made by consideringthe inertial mass of the mass body. For example, the ratio R/r ispreferably replaced by a ratio 2R/3r in the embodiments shown in FIGS.3(a) to 4(b) to take the inertial mass into consideration. In this case,the equation (1), which represents the torque T when the peak of torquefluctuations is equal to the characteristic frequency of the rollers, isreplaced by the following equation (2).

T=(3/2)m(ω^(a))²(R+r)Rφ  (Equation 2)

[0114] When a ball is used as a mass body that swings along the guidesurface (65, 82), the ratio R/r is replaced by a ratio 5R/7r for takingthe inertial mass into consideration. In this case, the equation (1),which represents the torque T when the peak of the torque fluctuationsis equal to the characteristic frequency of the mass body, is replacedby the following equation (3).

T=(7/5)m(ω^(a))²(R+r)Rφ  (Equation 3)

[0115] If a mass body the shape of which is not cylindrical or sphericalis used, the inertial mass of the mass body is preferably considered indetermining various settings for improving the resonance reductionperformance.

[0116] The pulley 17, 60 may be used for a double-headed piston typecompressor. In a double-headed piston type compressor, two compressionchambers are defined in each cylinder bore at both ends of thecorresponding piston.

[0117] The present invention may be applied to a compressor other thanthe compressor C. For example, the present invention may be applied fora wobble plate type compressor, in which a drive plate is rotatablysupported by a drive shaft.

[0118] The present invention may be embodied in a fixed displacementtype compressor.

[0119] The embodiments of FIGS. 1 to 9 may be applied to a scroll-typecompressor.

[0120] The embodiments of FIGS. 1 to 9 may be applied to any type ofrotation apparatus as long as the apparatus includes a rotary shaft anda pulley that rotate integrally, and torsional vibration is produced inthe rotary shaft.

[0121] In the embodiments shown in FIGS. 1 to 9, the center of swingingmotion of the mass body (the rigid pendulum 46, the roller 67, 83) neednot be parallel to the rotation axis of the pulley body 42, 61. The axisof the swinging motion may be inclined relative to the rotation axis ofthe pulley body within a range where a predetermined torque fluctuationreduction performance is obtained. If the axis of the swinging motion isinclined with respect to the rotation axis of the pulley body, adistance Rs, which will be discussed later, is used as the distancebetween the center of the swinging motion and the rotation axis of thepulley body. The distance Rs represents the distance between a point atwhich the axis of the swinging motion intersects a plane that isperpendicular to the swinging motion axis and a point at which the planeintersects the rotation axis of the pulley body.

[0122] The embodiments shown in FIGS. 1 to 9 may be applied to asprocket of a gear.

[0123] The mass body (the rigid pendulum 46, the roller 67, 83) may beattached to a rotating member accommodated in the housing of thecompressor C such as the lug plate 19 or other member for reducing therotational vibration produced in the drive shaft 16.

[0124] In the embodiments shown in FIGS. 1 to 4(b), the fluorocarbonresin forming the coating is preferably polytetrafluoroethylene.Compared to other fluorocarbon resin, polytetrafluoroethylene has betterlubrication characteristics.

[0125] In the embodiment shown in FIGS. 1 to 2(b), a fluorocarbon resincoating may be formed at the contacting parts of the pendulum 46 and thehead of the support shaft 47. Also, fluorocarbon resin coating may beformed at the contacting parts of the pendulum 46 and the pulley body42.

[0126] In the embodiment of FIGS. 1 to 2(b), fluorocarbon resin coatingmay b formed on the support shaft 47.

[0127] In the embodiments shown in FIGS. 3(a) to 4(b), fluorocarbonresin coating may be formed only on a part of the roller (67, 83) thatcontacts the guide surface (65, 82). Alternatively, fluorocarbon resincoating may be formed only on a part of the recess (64, 80) thatcontacts the facing surface or the lid 68.

[0128] In the embodiments shown in FIGS. 3(a) to 4(b), fluorocarbonresin coating may be formed on a surface that is a part of the recess(64, 80) or on a part of the lid 68 that contacts the roller (67, 83).

[0129] In the embodiments shown in FIGS. 1 to 9, the wear reductionmember is fluorocarbon resin coating. However, the wear reduction memberis not limited to the fluorocarbon resin coating. Any material or methodmay be used as the wear reduction member as long as the means reduceswear caused by contact between the pulley body 42, 61 and the mass body(the pendulum 46, the roller 67, 83), prevents the resonance reductionperformance of the swinging motion from deteriorating due to wear, andprevents the life of the pulley 17, 60 from being shortened. The coatingmay include a resin binder and a solid lubricant. Specifically, thesolid lubricant contained in the coating may be, for example, molybdenumdisulfide, tungsten disulfide, lead, indium, tin, graphite, boronnitride, antimony oxide, and lead oxide.

[0130] In the embodiments of FIGS. 1 to 9, as the wear reduction member,hard anodic oxide coating may be formed on the mass body (the pendulum46 or the roller 67, 83) and the pulley body 42, 61. In this case, sincethe hard anodic oxide coating is formed on the contacting parts of themass and the pulley body 42, 61, the surface of the mass body and thepulley body 42, 61 are hardened and wear resistance is improved.

[0131] In the embodiments of FIGS. 1 to 9, the surface of the mass body(the pendulum 46, the roller 67, 83) and the surface of the pulley body42, 61 may be modified and hardened for forming the wear reductionmember. In this case, the contacting parts of the mass body (thependulum 46, the roller 67, 83) and the pulley 17, 60 are hardened andthe wear resistance is improved.

[0132] In the embodiments of FIGS. 1 to 4(b), the entire pulley body 42,61 may be made of sintered material containing lubricant. Further, onlypart of the pulley body 42, 61 that contacts the mass body (the pendulum46, the roller 67, 83) may be made of sintered material. Also, in theembodiment shown in FIGS. 1 to 2(b), only the support shaft 47 may bemade of sintered material.

[0133] In the embodiments of FIGS. 3(a) to 4(b), the lid 68 may be madeof the sintered material. In the embodiments of FIGS. 1 to 4(d), theentire mass body (the pendulum 46, the roller 67, 83) may be made of thesintered material. Alternatively, only part of the mass body (thependulum 46, the roller 67, 83) that contacts the pulley body 42, 61 maybe made of the sintered material. Also, the entire surfaces of the massbody (the pendulum 46, the roller 67, 83) may be made of the sinteredmaterial.

[0134] The lubricant used in the illustrated embodiment may be liquidsuch as lubricant oil or solid. Solid lubricant is made of, for example,ethylene tetrafluoride, molybdenum disulfide, tungsten disulfide, lead,indium, tin, graphite, boron nitride, antimony oxide, and lead oxide. Inthis case, the lubricant contained in the sintered material reducesfriction resistance between the pulley body and the mass body, and thusreduces wear.

[0135] In the embodiment of FIGS. 4(a) to 4(b), an independent membermade of sintered material containing lubricant may be used as a part ofthe pulley body 61, and the recess 80 may be formed in this member.

[0136] In the embodiments of FIGS. 1 to 9, liquid lubricant such aslubricant oil may be applied to the contacting parts of the pulley body42, 61 and the mass body (the pendulum 46, the roller 67, 83). Theliquid lubricant preferably has low viscosity. This is because the lowerthe viscosity of a lubricant is, by the smaller degree the lubricanthinders the swinging motion of the mass body (the pendulum 46, theroller 67, 83). In this structure, the liquid lubricant reduces thefriction resistance between the pulley body 42, 61 and the mass body(the pendulum 46, the roller 67, 83), and thus reduces wear.

[0137] Therefore, the present examples and embodiments are to beconsidered as illustrative and not restrictive and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalence of the appended claims.

1. A compressor having a pulley for transmitting torque from an externaldrive source to a rotary shaft to drive a compression mechanism, whereinthe pulley has a pulley body, the compressor comprising: a mass bodylocated in a range that is radially inward of the outer circumference ofthe pulley, wherein the mass body swings about an axis that is spacedfrom the rotation axis of the pulley body by a predetermined distanceand is substantially parallel to the rotation axis of the pulley body.2. The compressor according to claim 1, wherein the mass body is a rigidbody that is rotatably supported by the pulley body.
 3. The compressoraccording to claim 1, wherein the pulley body has a guide portion thatguides the mass body, wherein the guide portion has a guide surfacehaving an arcuate cross section, wherein the mass body is a rigid bodythat has a circular cross section, and wherein the mass body moves alongthe guide surface.
 4. The compressor according to claim 3, wherein theguide portion has an inner surface having an arcuate cross section, andwherein the guide surface is a part of the inner surface.
 5. Thecompressor according to claim 1, wherein the ratio of the distancebetween the axis of the rotary shaft and the axis of the swinging motionof the mass body to the distance between the axis of the swinging motionof the mass body and the center of gravity of the mass body isdetermined such that the frequency of the greatest peak of fluctuationsin the torque transmitted to the pulley body is equal to thecharacteristic frequency of the mass body.
 6. The compressor accordingto claim 1, wherein the mass body is one of a plurality of mass bodies,wherein one of the mass bodies is configured such that the ratio of thedistance between the rotation axis of the pulley body and the axis ofthe swinging motion of the mass body and the distance between the axisof the swinging motion of the mass body and the center of gravity of themass body is different from those of the other mass bodies.
 7. Thecompressor according to claim 1, wherein the compression mechanism is apiston type compression mechanism for compressing fluid based onreciprocation of the piston, wherein the piston is accommodated in acylinder bore.
 8. The compressor according to claim 1, wherein at leastone of the pulley body and the mass body includes a wear reductionmember for reducing wear due to contact between the pulley body and themass body.
 9. The compressor according to claim 8, wherein part of thepulley body that contacts the mass body is formed with metal and theother part of the pulley body is formed with resin.
 10. The compressoraccording to claim 8, wherein the wear reduction member is a coating,and wherein the coating is formed on one of the surface of the pulleybody and the surface of the mass body.
 11. The compressor according toclaim 10, wherein the coating includes solid lubricant.
 12. Thecompressor according to claim 8, wherein the wear reduction member isliquid lubricant.
 13. The compressor according to claim 8, wherein thewear reduction member is a sintered member containing lubricant.
 14. Thecompressor according to claim 8, wherein the wear reduction member is aresin containing lubricant.
 15. A pulley for a compressor, comprising: apulley body; a mass body located in a range that is radially inward ofthe outer circumference of the pulley, wherein the mass body swingsabout an axis that is spaced from the rotation axis of the pulley bodyby a predetermined distance and is substantially parallel to therotation axis of the pulley body.
 16. The pulley according to claim 15,wherein the mass body is a rigid body that is rotatably supported by thepulley body.
 17. The pulley according to claim 15, wherein the pulleybody has a guide portion that guides the mass body, wherein the guideportion has a guide surface having an arcuate cross section, wherein themass body is a rigid body that has a circular cross section, and whereinthe mass body moves along the guide surface.
 18. The pulley according toclaim 17, wherein the guide portion has an inner surface having anarcuate cross section, and wherein the guide surface is a part of theinner surface.
 19. The pulley according to claim 15, wherein at leastone of the pulley body and the mass body includes a wear reductionmember for reducing wear due to contact between the pulley body and themass body.
 20. The pulley according to claim 15, wherein the ratio ofthe distance between the rotation axis of the pulley body and the axisof the swinging motion of the mass body to the distance between the axisof the swinging motion of the mass body and the center of gravity of themass body is determined such that the frequency of the greatest peak offluctuations in the torque transmitted to the pulley body is equal tothe characteristic frequency of the mass body.
 21. The pulley accordingto claim 15, wherein the mass body is one of a plurality of mass bodies,wherein one of the mass bodies is configured such that the ratio of thedistance between the rotation axis of the pulley body and the axis ofthe swinging motion of the mass body and the distance between the axisof the swinging motion of the mass body and the center of gravity of themass body is different from those of the other mass bodies.